1. Field of the Invention
The invention relates to a filter aid, a process for its production and its application.
2. Description of the Related Art
Cellulose-based filter aids have been known for a long time (“Ullmann's Encyklopädie der Technischen Chemie”, 3rd edition (1951), first volume, page 492, key word “felted layers” and page 493, key word “filter aids”). Cellulose is produced in a multi-step chemical process, in which all sensorially active materials are removed from the raw material.
Hence filter aids made of pure cellulose are used wherever the sensorial neutrality of the used filter aid is of great significance. Examples of cellulosis filter aids are EFC (low extract cellulose), fine powder cellulose, fine fibrillated cellulose cationized powder cellulose, fine MCC (microcrystalline cellulose).
In contrast, filter aids made of untreated woodpulp are produced by mechanical comminution, thus only by physical treatment, and can, thus, release extractives (color, odor, flavor) during filtration. Therefore, the use of wood fiber-based filter aids is usually limited to industrial filtrations, where relatively little demand is placed on the sensory analysis.
Not only for filtration in the food and luxury food sector, but also for many industrial applications, they may not be considered, e.g. for sugar solutions (glucose, dextrose, fructose), molasses, dye solutions, fats and oils and the like.
The difficult field of beverage filtration demands, on the one hand, complete sensorial neutrality of the used filter aid; on the other hand, the number of commonly used filter aids are limited for economic reasons, since the maximum expense for the filter aid is fixed by the price of the mineral filter aids dominating this market.
Usually beer filtration take place in two steps. The first step usually involves a coarse filtration, during which operation the liquid usually passes through a precoated layer of a filter aid. This step is frequently followed by a fine filtration (membrane, kieselguhr, etc.).
The standard filter aid for the precoat-type filter in the beverage, especially beer, sector, is kieselguhr. A high percentage of the world beer production is clarified by kieselguhr filtration. Currently it exceeds more than 1.1 billion hecto liter of beer.
The total demand for filter aids is worldwide ca. 750,000 tons per year, where inorganic materials, like, for example, kieselguhr, perlite or bentonite, constitute by far the largest share of this amount. Of this total amount about 250,000 tons to 300,000 tons per year are consumed worldwide by the beverage industry, largely by the breweries, but also by producers of wine and fruit juices.
The amount of filter aids, which are based on organic raw materials that can regrow again (cellulose, woodpulp, etc.), is to date only ca. 20,000 tons per year, even though their use offers a plurality of advantages over inorganic filter aids.
Thus organic filter aids are natural materials, whose quality fluctuates only over a narrow range and whose occurrence can be renewed at regular intervals. In addition the use of organic filter aids presents neither a health risk nor harmful effects for the environment and nature. Pumps and conveying elements of the filtration system are protected as much as possible owing to the non-abrasive property. Finally the consumed filter cakes can be easily disposed, for example, through land management, composting or animal fodder.
Of course, organic filter aids are in part many times more expensive than kieselguhr or they exhibit filtration properties that do not completely match those of kieselguhr.
For this reason organic filter aids have not been able to prevail to date against kieselguhr or are used in any case together with kieselguhr (report by J. Speckner “Cellulose as Filter Aids” in the journal (“Brauwelt”, vol. 124 (1984), issue 46, pages 2058 to 2066, in particular page 2062, left column top).
However, kieselguhr has become increasingly a problem. As a natural mineral material its occurrence is limited. Thus in the case of kieselguhr one must resort more and more to low grade qualities in order to meet the high demand of industry. The result is, however, a rising cost for the cleaning and processing of kieselguhr, which could in the long run have a negative impact on its economic, situation.
An even greater impact presents, however, the fact that the users' attitude towards kieselguhr is becoming more critical.
This reservation stems from the problems posed to the lungs due to many natural mineral materials and hence kieselguhr, a feature that must be taken very seriously from the point of view of occupational medicine. In 1988 the World Health Organization (WHO) categorized kieselguhr as a carcinogenic substance following a series of animal experiments. For handling there are strict regulations that are being asserted and observed more and more in Germany.
Another factor is that the disposal of kieselguhr is becoming increasingly more critical in industrial countries. A classification as hazardous waste makes landfilling considerably more difficult. With the introduction of the new technical rules on municipal waste, the disposal situation for kieselguhr is becoming more restrictive. In many cases, disposal of kieselguhr used as filter aid already gives rise to costs of approximately DM 600,000 per ton of kieselguhr, if this was used in beer filtration, or 1500.00 per ton of kieselguhr if this was used in the industrial filtration of problematic substances.